I like to have the piece of mind of having the synthetic jacket as insurance against the unlikely possibility of having a wet down sleeping bag.

Like anything else, you have to look at where you are traveling to on your trips to see if an all down sleeping system and down insulating layer makes sense…if you are in a very dry area, with a low to no chance of rain, then an all down setup might make sense for weight savings.

The synthetic jacket will give you a weight penalty vs. a down one, but think of it as extra insurance and piece of mind.

I have both. I used to think along the same lines as Tony but the down is warmer for the weight and I've never gotten anything inside the protected area of my pack wet. If I planned on 10 + days of sustained cold rain or wet snow I'd take all synthetic, including quilt or bag.

It really all depends on the odds of rain on your trip, or how many rivers you will be crossing. i.e. what are the odds of your bag getting wet. I have a MB Down Inner Parka and it comes with me on every trip. It's perfect for 3-season backpacking. I also have an Outdoor research synthetic parka for winter/wet backpacking.

The odds of my sleeping bag getting wet are small. I put it in a BPL liner for any trip with no predicted rain. Sierra storms are intense but brief so that would be fine. If rain was predicted, or if I was fording rivers more than knee deep, I'd get a dry sack. The down jacket goes in an Event stuff sack with my NeoAir and baselayers, so it's not getting wet, period.

So I personally don't worry too much about a 'safety' synthetic layer. But I also only do 1-3 night trips as of now, so I'm never so far that bailing out in the unlikely case of wet down would be life threatening. Outside of pretty extreme conditions, you could probably survive one night doing situps/jumping jacks without getting hypothermic and bail out in the morning.

For a longer trip, getting farther out, I'd likely bring the OR parka as a safety measure.

Tony, I agree and think that's a good strategy to mix the two so you always have a fail safe if your down gets wetted out.

Since I don't expect to be doing anything extreme and most of my backpacking is late spring, summer and early fall on shortish trips no longer than 3 days, I think down might be a good choice.

I'm going to go with the MB inner down parka and then when the Cocoon '10 line comes out, I can grab a synthetic layer too. No sense getting a synthetic jacket when BPL will make me want to upgrade when the new jackets come out.

Thanks guys.

Incidentally, even though there were multiple replies to this thread, I only got one email notice for watching this thread…